Enhanced high-rate performance in Zn/Al dual-doped LiMn2O4 with submicron truncated structure
The Jahn-Teller effect and Mn dissolution always restrict the practical electrochemical properties of spinel LiMn 2 O 4 cathode material. Herein, a low-temperature solid-state combustion method is employed to synthesize various truncated octahedral LiZn 0.03 Al x Mn 1.97- x O 4 ( x ≤ 0.08) with submicron structure. The Zn/Al dual-doping is conducive to forming {110} and {100} planes, and is also beneficial to the crystal development of LiMn 2 O 4 . It is found that as the amount of Al doping increases, the average particle size gradually decreases from 188 nm to 113 nm. In addition, the Zn/Al co-doping integrated with small particles can improve the high-rate performance. The optimal LiZn 0.03 Al 0.03 Mn 1.94 O 4 exhibits submicron truncated octahedral morphology, high crystallinity , and good particles dispersibility . Benefiting from these structure merits, the LiZn 0.03 Al 0.03 Mn 1.94 O 4 delivers the first discharge capacity of 113.1 mAh⋅g −1 and low capacity fade of 9.9 % after 300 cycles at 1C. It also shows the high first discharge capacity of 86.6 mAh⋅g −1 at 10C and the high capacity retention of 72.1 % after 2000 cycles. Even at ultrahigh current density of 15C and 20C, the ultralong cycling lifespans over 2000 cycles are also achieved in LiZn 0.03 Al 0.03 Mn 1.94 O 4 cathode material. The excellent electrochemical properties are ascribed to its relatively high Li + diffusion coefficient (1.60 × 10 −11 cm 2 ⋅s −1 ) and low apparent activation energy (25.45 kJ⋅mol −1 ) during the de-intercalation process. The Zn/Al dual-doping and submicron truncated octahedron designs of the LiMn 2 O 4 provide a scientific reference to prepare high-performance cathode materials.
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